I was recently looking through some of the books that my school's library was selling, when my eye was caught by one with the title of Tube Lore. I bought it promptly, and went off to read it. It contains a listing of registration numbers for and descriptions of just about every electron tube that has ever been commercially available. It has information and exact specifications on just about every magnetron, klystron, microwave triode, CRT displays, ect., that is out there. I could not find an electronic version of this book, but you can find it online and buy it, as it can immensely help in the search for just what a certain tube you purchased from a surplus bin does.

There are a good few of us old tube lovers out here, my own collection is over 7000 pieces.
Some RCA tube handbooks are online, radio am handbooks have some info, and so on.
Here's a data sheet link that I find useful:

which is a site for tubers, some of which are still finding new tricks for old dogs, and JoeS is one of the best at that, the kind of guy who thinks dreaming up a two tube relfex superhet is still fun -- especially if that tube radio can run on an aa cell and a 9v battery.
Lots of fun stuff there, and a lot of clever ideas.

I am right now looking at some interesting and obscure tubes for fusor uses, as they are small and can stand being right in the tank as preamps, unlike just about any solid state. There are some electrometer tubes that came in old (otherwise useless) ion chamber detectors that may do, and some very interesting Russian sub-sub mini tubes that were used until recently in avionics that have fantastic specs and low enough power dissipation that they'd work too. Ceramic feedthroughs have a lot of leakage current, and the wires to them get hit enough by stray ions to necessitate some kind of preamp for certain things. You can't always use say, a channel multiplier, so I look at other possible approaches. A Russian rod pendode with micron electrode spacings that uses 20mw to run is looking pretty decent, for example. You can get rid of that kind of heat by clamping to the tank wall.

Any solid state device there would have to be 100% encapsulated in solid copper, clamped to the wall, and "heroic" measures used as protection on any input and output leads, or it will die, and right away. Not to mention, a hot particle may make it into a detector of something you don't want in the desired signal. Just try it if you're not a believer. No such problems with tubes.

Nope, I'm suggesting a preamp for signals of such low levels they won't go through a ceramic feedthrough without degradation, as I explicitly stated with some detail.

Heat is so hard to get rid of in a vacuum that power sorts of things -- forget it, mostly. If you have to conduction cool through the tank walls, you suddenly have an insulation problem, right?

Though for RF kinds of things (think tesla secondary or Pi network) that don't dissipate much heat, you may have a case. But any power diodes won't live, including tube types. For most of the HV ones, the filament current alone will be enough heat to burn it up, even if you rid it of the base and other lower temperature external parts. For SS ones, there's this problem of forward drop and reverse recovery power waste -- same troubles -- heat == death.

Even a low power opamp will just burn up if not conductively cooled some way. It's the principle pirani gages work on, after all.

Comsat used to teach a course on this, for electronics in vacuum. It's quite an eye opener. I have no idea if the course materials are available or maybe classified. I took the course as part of prep to design things for space environments. Even NASA regularly forgets this kind of thing when they mis-apply the "better cheaper faster" mantra and try to use COTS parts in space.

We have a much worse vacuum than space, (not so much so when it comes to heat) but we also have a lot of other constraints a satellite doesn't -- along with some freedoms they don't -- we can open the tank and fix things. This is hard stuff to get right, and no guessing can be involved if you want it to live.

I don't mean to hijack the thread, but wanted to say this is interesting stuff, at least to me. A few years back I did up some down hole instruments using the tubes with leads (we used to call them "peanut" tubes, but I've noticed some radio collectors referring to some other antique tube as a "peanut" tube) and some nuvistors to withstand the heat, which was killing the IC probes the company was using. Later on I adapted this same tube topology to some sampling equipment used in bore holes around radiation waste storage sites. The close in sensors were falsifying data far too often. I used a 5886 tube from the surplus survey meters back when I was experimenting with electrostatic lifters to make an ion meter. I guess the last thing I've done with the peanut tubes was to make a tube output stage for a CD audio player. Great stuff. I have a large selection if you're looking for anything let me know.

Doug Couter wrote:Nope, I'm suggesting a preamp for signals of such low levels they won't go through a ceramic feedthrough without degradation, as I explicitly stated with some detail.

Heat is so hard to get rid of in a vacuum that power sorts of things -- forget it, mostly. If you have to conduction cool through the tank walls, you suddenly have an insulation problem, right?

Though for RF kinds of things (think tesla secondary or Pi network) that don't dissipate much heat, you may have a case. But any power diodes won't live, including tube types. For most of the HV ones, the filament current alone will be enough heat to burn it up, even if you rid it of the base and other lower temperature external parts. For SS ones, there's this problem of forward drop and reverse recovery power waste -- same troubles -- heat == death.

Even a low power opamp will just burn up if not conductively cooled some way. It's the principle pirani gages work on, after all.

Comsat used to teach a course on this, for electronics in vacuum. It's quite an eye opener. I have no idea if the course materials are available or maybe classified. I took the course as part of prep to design things for space environments. Even NASA regularly forgets this kind of thing when they mis-apply the "better cheaper faster" mantra and try to use COTS parts in space.

We have a much worse vacuum than space, (not so much so when it comes to heat) but we also have a lot of other constraints a satellite doesn't -- along with some freedoms they don't -- we can open the tank and fix things. This is hard stuff to get right, and no guessing can be involved if you want it to live.

+++

I remember old 4 pin valves that used a simple straight central filament/cathode coaxial with a helical grid that was, in its turn, coaxial with the tubular anode. The electrode spacing was a lot bigger than seen in modern devices, so it would be easire for the amateur to fabricate.

Could such a structure not be built as a preamp (with electrostatic screening) inside the experimental tube?